During later years, compounds having blocking activity on the .beta.-adrenergic receptors having gained increasing importance, i.a. as tranquilizers and medicines against various heart and vascular diseases such as heart arrythmias, and angina pectoris. It has been established that there exist two types of .beta.-receptors, for convenience called .beta..sub.1 -receptors and .beta..sub.2 -receptors. .beta..sub.1 -receptors are predominant, i.a., in the heart and .beta..sub.2 -receptors predominant, i.a., in the bronchia and blood vessels. It has also been established that some compounds act more or less indiscriminately on both types of .beta.-receptors; an outstanding example of this type of compounds is propranolol, i.e., 1-(isopropylamino)-3-(1-naphthyloxy)-2-propanol. Other compounds have a blocking activity predominantly on either the .beta..sub.1 -receptors or the .beta..sub.2 -receptors. If a compound has blocking activity on the .beta..sub.1 -receptors and not on the .beta..sub.2 -receptors it can be considered promising as a drug for the treatment of, i.a., hypertension and is furthermore likely to be tolerated by asthma patients. An example of a compound having substantial blocking activity on the .beta..sub.1 -receptors and not on the .beta..sub.2 -receptors is practolol which suffers, however, from the disadvantage that it has some intrinsic effect and side effects. Great effort have been made to find compounds having a high specificity for blocking .beta..sub.1 -receptors and being free from side effects and intrinic effects on the .beta.-receptors and also requiring small dosages, i.e. being highly active.
A rather recent development in the field of compounds having .beta.-adrenergic blocking activity is represented by Belgian Pat. No. 811,274 to Ciba-Geigy AG. It claims a large number of compounds including compounds having the general formula ##STR3## wherein Het (amongst other possibilities) is a substituted pyridyl radical, R.sup.a a hydrogen atom or a methyl group, and R.sup.b (amongst other possibilities) a lower alkyl group. Accordingly, a compound of formula I above wherein R is hydrogen, is not claimed. A compound of formula I wherein R is amino is claimed but not disclosed and probably not contemplated. The reason for this assumption is that a subclaim claims pyridyl derivatives of the formula ##STR4## R.sup.a and R.sup.b have, i.a., the above meanings, n is 1, 2, or 3 and wherein R.sup.c, amongst other meanings, may be alkyleneamino, thiaalkyleneamino, hydroxyalkyleneamino, alkylamino, dialkylamino, acylamino, but not unsubstituted amino; of course, no compound with such an unsubstituted amino group is disclosed.